I. Field
The present invention relates generally to telecommunications, and, more specifically, to power savings for wireless devices employed in wireless communication systems and cellular communication systems.
II. Background
A modem communication system provides data transmission for a variety of applications, including voice and data applications. In point-to-multipoint communications, modem communication systems have been based on frequency division multiple access (FDMA), time division multiple access (TDMA), code division multiple access (CDMA), and other multiple access communication schemes.
A CDMA communications system is typically designed to support one or more CDMA standards, such as (1) the “TIA/EIA-95 Mobile Station-Base Station Compatibility Standard for Dual-Mode Wideband Spread Spectrum Cellular System” (this standard with its enhanced revisions A and B may be referred to as the “IS-95 standard”), (2) the “TIA/EIA-98-C Recommended Minimum Standard for Dual-Mode Wideband Spread Spectrum Cellular Mobile Station” (the “IS-98 standard”), (3) the standard sponsored by a consortium named “3rd Generation Partnership Project” (3GPP) and embodied in a set of documents known as the “W-CDMA standard,” (4) the standard sponsored by a consortium named “3rd Generation Partnership Project 2” (3GPP2) and embodied in a set of documents including “TR-45.5 Physical Layer Standard for cdma2000 Spread Spectrum Systems,” the “C.S0005-A Upper Layer (Layer 3) Signaling Standard for cdma2000 Spread Spectrum Systems,” and the “TIA/EIA/IS-856 cdma2000 High Rate Packet Data Air Interface Specification” (the “cdma2000 standard” collectively), (5) the 1xEV-DO standard, and (6) certain other applicable standards. The standards expressly listed above are incorporated by reference as if fully set forth herein, including annexes, appendices, and other attachments.
Generally, a wireless local area network (WLAN) Access Point provides data on the downlink to a user's wireless device, also called a station, or STA. The downlink transmission of large quantities of data from an Access Point to a STA can sometimes result in the STA remaining fully powered for extended periods of time due to uncertainty as to whether all data has been received from the upstream devices. As a result, such devices do not efficiently conserve power in the device.
Different power saving schemes have been devised. Various methods have been employed to address a wireless device transitioning to a power save mode after receiving large blocks of data on the downlink, i.e. from the Access Point. Such methods have included using power save indications on certain transmitted frames, and use of inactivity timers, wherein after a certain amount of inactivity the STA transitions to a power save mode. However, these designs either require additional bandwidth or processing, or employ timers in accordance with assumptions that may be invalid or unduly excessive.
In one available implementation, called PS-Polling, the STA goes into a sleep mode or state. The Access Point indicates the presence of data for the sleeping STA through the Traffic Indication Map (TIM) transmitted using the beacon signal which can be received by the sleeping STA. The STA, upon receiving the TIM indicating the availability of data at the Access Point, exists the sleep state and sends a Null frame with a Power Management “transition to active mode” indication. When the Access Point receives the Power Management transition event from the STA, such a WLAN arrangement has in the past computed a “worst case” delay time, wherein the STA waits for a relatively long amount of time, i.e. more time than is necessary in a worst case scenario, before again entering Power Save mode. Values considered include the amount of time needed to transmit the frame, the amount of delay resulting from channel interference and frame retries, and so forth, resulting in a relatively large inactivity period, i.e. a relatively large amount of time before Power Save again begins at the STA.
Therefore, there is a need for methods and apparatus that would reduce power consumption at the STA without excessively compromising performance characteristics of the STAs and of the radio networks with which the STAs communicate.